Steel making slag and clay mixtures (hereinafter referred to as “modified clay”), which are dredged clay mixed with steel making slag, are self-hardening, so unconfined compression strength is used for quality control as a geomaterial. The self-hardening properties of modified clay depend on the water content of dredged clay, properties of steel making slag, and mixing ratio. Therefore, mixing experiments to determine the mixing ratio of steel making slag are essential, and there is a desire to streamline these experiments. In this paper, the results of mixing experiments of improved clay mixed with different types of steel making slag using dredged clay with different water content as the base material are rearranged, and a method to evaluate the relationship between mixing ratio and unconfined compression strength in a unified manner is discussed, and the following results were obtained. 1) To achieve the desired strength as modified clay, a certain amount of modifying agent must be added. 2) The relationship between slag-clay mass ratio and unconfined compression strength was different for each condition, but the relationship between slag-clay mass ratio and unconfined compression strength normalized by unconfined compression strength for a given slag-clay mass ratio was a univocal relationship.
